The Evolutionary Mismatch of Sedentary Lives

“This seems like a landmark paper in my books and a call from the other side of the energy balance equation. We seem built to be a highly physically active species, not sedentary office workers and couch dwellers.” With these words, Professor Emeritus Jennie Brand-Miller seized our attention today. She was writing about a new paper by a distinguished team of evolutionary biologists and physiologists. By Andrew Yegian and colleagues, it appears in the Proceedings of the National Academy of Sciences. It tells us that humans have evolved a metabolic rate distinct from all other mammals. Uniquely high, it is a profound evolutionary mismatch for sedentary lives, as the authors explain:

“Postindustrial societies are characterized by declining levels of physical activity combined with increased food energy availability and adiposity and more time in thermoneutral environments from air-conditioning and heating.

“Persistent sedentariness is thus an evolutionary mismatch. By spending less energy on physical activity which allocates energy toward repair and maintenance mechanisms, sedentary individuals funnel more energy toward excess fat storage and higher levels of reproductive hormones.”

Sweat Sets Humans Apart

Yegian describes the uniquely human metabolic profile:

“Humans have increased not only our resting metabolisms beyond what even chimpanzees and monkeys have, but – thanks to our unique ability to dump heat by sweating – we’ve also been able to increase our physical activity levels without lowering our resting metabolic rates.

“The result is that we are an energetically unique species.”

In sum, human metabolism evolved to favor high brain function, faster reproductive rates, extended longevity, and a high percentage of body fat. But we are not so well adapted to sit still in a temperature-controlled environment.

The Misleading Label of Diet-Related Diseases

Much of the thinking about obesity and its consequences for health employs a shorthand that labels all of this as “diet-related” diseases. But in the light of these evolutionary insights, that label may be profoundly misleading.

Obesity has not risen simply because we are eating too much of the wrong things. Nor is it because big food is “poisoning” us. In fact, it might be more informative to label these diseases as technology-related.

In that way, we can point to the full range of technologies creating the evolutionary mismatch of our sedentary lives. Food technology is just one part of the picture.

Click here for the new paper in PNAS and here for further perspective.

The Wedding of the Bohemian, painting by Edvard Munch / WikiArt

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December 3, 2024